On the command line, I used format override fs=fat32 while in diskpart, assuming I had selected my 8GB flash drive, and realised I'd accidentally selected my 2TB external drive which had been assigned the same number after reboot (it's been a long night).

The format ran for about a minute or so, without progressing to 1%, before I realised what I'd done and did CtrlC.

The external drive no longer shows up in My Computer, even after a reboot of my computer, although it is visible in Device Manager.

As you can imagine, I'm panicking a fair bit right now, fearing I've lost a terabyte and a half of data - no backups of this particular drive, obviously.

Any help - and assurance that I haven't lost anything or wrecked my drive - would be vastly appreciated. Thanks.

Update 1: In diskpart, doing list volume, selecting the raw volume with select volume #, and then doing assign assigns it a drive letter, making it discoverable to Explorer and in My Computer, although it then gives the error that it needs to be formatted. From thereon, clicking on the drive in My Computer returns the error:

H:\ is not accessible

The parameter is incorrect.

Update 2: Running the trial ("Simple") version of GetDataBack on the drive took around 26 hours, and returned at least a hundred different sectors of varying sizes, including large FAT32 and NTFS sectors.

Update 3:

Doing some detailed digging into the results of GetDataBack's thorough search showed me the full list of filesystems. Shockingly, buried in that list I found a 1.82 TB sector, which roughly corresponds to the size of my lost data. It's likely that this is it, and that all I now need to do is to recover to it to get 99% of my files back, but I'm hesitant to do anything before I understand what the other file systems are and why they're so large. The Ext filesystem registers as over 500GB, for example, and several other NTFS filesystems are over 400GB. Does anyone have any idea what these other file systems may be?

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    Wait wait wait... Windows 7 cannot format a 2TB volume as FAT32, it simply won't do it because the volume is too large (Windows' max is 32 GB for FAT32). I reckon all that happened is that the "override" argument forced the volume to dismount. So you lost the drive letter, no big problem, you can go back into diskpart and "list volume", select the volume without a drive letter and then "assign letter=x" to get it back. Good luck!! – misha256 Jul 19 '17 at 2:34
  • Damn, you got my hopes up. I tried doing that, and it came back successful, but then I got this: imgur.com/a/ZAAx5. – Prometheus Jul 19 '17 at 2:39
  • imgur.com/a/4w3Gk It's now at least showing up in My Computer, but clicking on it comes back with the format dialogue seen above. – Prometheus Jul 19 '17 at 2:41
  • Scratch that, it now results in a complete dead end: imgur.com/a/xvpMd. – Prometheus Jul 19 '17 at 2:42
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    Yeah there we go I would bet the CLEAN command you actioned was against the hard drive too. CLEAN does this: Removes any and all partition or volume formatting from the disk with focus. On master boot record (MBR) disks, only the MBR partitioning information and hidden sector information are overwritten. I think it's time you started looking at recovery tools to get your data back. – misha256 Jul 21 '17 at 0:10

So you potentially have a disk that is partly NSTF and partly FAT32. What you would want to do is trick the PC into reading it as NSTF even though it partly FAT32 now.

Have you tried a tool like Piriform's Recuva?

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  • I see EaseUS has a tool claiming to help in a situation like this as well. You may need to remove the disk and plug it into a USB Hard Drive dock to get it recognized. – tekFranz Jul 19 '17 at 2:24
  • The HDD is plugged out and sitting quiet for now, it was making some odd boot noises and I feel like the longer it's on the more likely it is to get worse. I haven't tried any recovery tools yet because I'm banking on the possibility it won't be needed and that a more simple, less painstaking solution is still on the table, especially given how little time the format was running for. – Prometheus Jul 19 '17 at 2:29
  • I read something online that if a drive simply isn't showing up in My Computer, but is visible in Device Manager and in diskpart itself, it simply needs a drive letter assigned to it to be recognised by My Computer again. Could it be that simple? Would using diskpart's assign command work? – Prometheus Jul 19 '17 at 2:33
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    Any idea the type of Master File Table it had and if it can be recreated? It seems like that may be the only thing affected. – tekFranz Jul 19 '17 at 2:47
  • What exactly do you mean by type? And how would I go about recreating one if I did know? – Prometheus Jul 19 '17 at 20:48

I can appreciate all the help you are receiving here. But, if you started formatting the partition then you probably immediately overwrote the master file table. The file table is what tell Windows where each piece of every file on the physical drive is located and which files and folders exist. Kind of like a card catalog at the library.

Without that, there is no simple way to get your files back. You'll have to use a data recovery tool to try to look for the files manually. The tool you said you used sounds like it is trying to restore a deleted partition. That is the wrong kind of scan. You don't have a deleted partition and you can't "restore" the drive to normal operation.

Your only option at this point is to manually scan for any files and see if they can be recovered. A tool like Recuva (as suggested earlier) has given me good success. I've also used File Scavenger with great success. It will identify the files it can find and tell you if they are recoverable or not.

Unlike a library with a missing card catalog, your "books" aren't all in one piece if the drive is fragmented. This means there is a large possibility only smaller, non-fragmented files can be recovered. There is some plus to this, because most of absolutely non-replaceable data is small in size (pictures, word documents, etc.)

What hasn't been mentioned is that if you write anything to the drive you are damaging your chances of recovery. Professionals clone the drive first so they don't mess with the original. You have to be absolutely sure you are not writing anything back to the drive. All files restored need to be restored to a different drive, and NEVER EVER use any tool to "repair" a drive if it is your only copy of the data.

You also mentioned noises and concerns about making things worse by letting the drive run. This is a totally separate issue. Your drive isn't going bad because you formatted it or leave it plugged in. If it has other physical problems, then you've just compounded the difficulty of this recovery exponentially.

Also, if this data is really, really important to you then you should definitely NOT be attempting any data recovery on it. Send it to a professional.

I don't want to sound like I'm saying told you so, but I hope this is a lesson learned, and a lesson for all other readers - BACKUP YOUR DATA. It's unbelievable how many people have critical, can't possibly lose it, it's the end of my life as I know it data, but don't back it up.

Best of luck to you.

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  • If the tool you're referring to is GetDataBack, it is indeed a data recovery tool. When researching the best one to use, it came back more highly recommended than Recuva, which is why I started using it. Good shout on the noises, it isn't physically damaged so it should be okay in that sense. You're right that I probably should have cloned the drive and worked on the cloned image, but GetDataBack claims to be a read-only tool, so it should be fine in that sense. There are three steps to GDB: scanning the drive, selecting file system fragments/sectors as indicated... – Prometheus Jul 21 '17 at 19:11
  • ...in this image, and recovering files from within those file system fragments. I'm just unsure on the specifics of how exactly the second step works, and was hoping someone here could enlighten me - specifically on whether I'm limited to selecting one file system fragment and copying the data from that alone, or whether I can keep coming back to Step 2 to copy files from each file system sector. – Prometheus Jul 21 '17 at 19:13
  • From what you say about this not being a problem of lost partition tables, as @tekFranz believes it is, I assume that TestDisk would be unsuitable in this instance? – Prometheus Jul 21 '17 at 19:15
  • From my description of GetDataBack above, does Recuva function in a similar way, or is it simpler to use? – Prometheus Jul 21 '17 at 19:24
  • What I'm really confused about GDB is why it brings back significant portions of several different file systems. How is it possible for a single drive to contain large FAT32, NTFS and exFat partitions? – Prometheus Jul 21 '17 at 19:24

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